Objective Assessment of Area of Algae Eaten by Mayflies

Posted by Pete Cadmus on Jul 16, 2008; 2:38pm
URL: http://imagej.273.s1.nabble.com/Objective-Assessment-of-Area-of-Algae-Eaten-by-Mayflies-tp3695376.html

I am an ecologist trying to assess the amount of periphytic (surrounding rocks) algae that is eaten by mayflies.  I have cultured algae on 7/8” by 7/8” tiles.  I hope to photograph the tiles before the mayflies graze on them and after.  Then use ImageJ to asses the surface area of algae compared to the surface area that was grazed free of algae.  Unfortunately the algae is not able to be grown uniformly.  Algae can appear as thick dark green filaments to only slightly green/brown tinted film.  The tile appears as white.  Often where the insect grazes algae only a slight color difference exists between the white tile and very thin film of diatoms.  Also, I am working in a greenhouse so photos will have inconsistent lighting from day to day even under a hood.  

I have been reading your archive all day, I have learned a great deal, you are all doing some impressive work.  Can someone point me in the right direction as to what plug-ins to install and what process to follow.  What approach do you feel is the best, most objective way to asses the area grazed?

Thanks for your time,
Pete Cadmus
Graduate Student of Fish, Wildlife and Conservation Biology
Colorado State University
petecadmus( a  t ) hot mail (d o t) com
970-491-5563 lab
970-482-0784 home

P.S. I am happy to send sample photos of algae by email